I saw this posted internally and thought I would share.  If you have clients that think they are up to date, but WSUS does not, have a look at this KB and also try these commands:

940357  An update is available to enable automatic approval of definition updates and to fix two problems in the Update Services component of Windows Small Business Server 2003 R2 - http://support.microsoft.com/default.aspx?scid=kb;EN-US;940357

and

Wuauclt /detectnow /resetauthorization

or

wuauclt /reportnow

from a cmd prompt on the client box (elevated if running on Vista)

ttfn

David